Nuclear localization of STAT3. Localization in MM cell lines (A) and PBMCs and bone marrow CD138⁺ cells from healthy volunteers and from multiple myeloma patients (B-C). Enriched CD138⁺ cells from bone marrow aspirates of healthy volunteers and multiple myeloma patients were immunostained for STAT3 as described in “Patients, materials, and methods.” Red stain indicates the specific staining for STAT3, whereas blue stain indicates the relative position of the nuclei in the corresponding view. Patient's numbers are indicated above each panel in C. Original magnification, × 200.